As bandwidth demands have increased, service providers have looked for ways to increase data transmission performance over the copper wire local loop transmission lines that connect telephone central offices (COs) to customer premises (CPs). In conventional telephony networks, customer premises equipment (CPE) is coupled to CO switches over the copper wire local loop transmission lines, which are commonly known as “local loops,” “subscriber lines,” “subscriber loops,” “loops,” or the “last mile” of the telephone network. In the art, the term “line” and “loop” are used interchangeably, both terms referring to the copper wire pair used in a typical telephone transmission line conductor. Historically, the public switched telephone network (PSTN) evolved with subscriber loops coupled to a telephone network with circuit-switched capabilities that were designed to carry analog voice communications. “Central office” or “CO” includes any site where a subscriber loop couples to a telephony switching unit, such as a public switched telephone network (PSTN), a private branch exchange (PBX) telephony system, or any other location functionally coupling subscriber loops to a telephony network. The provisioning of digital service to the CP is a more recent development. With it, the telephone network has evolved from a system capable of only carrying analog voice communications into a system that can simultaneously carry voice and digital data.
Historically, the POTS subscriber loop was designed with the functions needed to communicate analog voice-conversation signals and subscriber loop signaling. The CO switch uses subscriber loop signaling to notify the customer premises about events in the telephone network, while customer premises equipment (CPE) use subscriber loop signaling to inform the CO to perform actions for the customer. Some examples of subscriber loop signaling include: the CO switch signaling to the CPE that an incoming call has arrived by ringing the phone, the CPE (e.g., a telephone) signaling to the CO switch that the CPE is initiating a call by an on-hook to off-hook transition of the telephone handset, and the CPE signaling to the CO switch that a call should be connected to a location by transmitting the phone number of the location.
Because of the prohibitive costs of replacing or supplementing existing subscriber loops, technologies have been implemented that utilize existing subscriber loops to provide easy and low cost migration to digital technologies. Subscriber loops capable of carrying digital signals are known as digital subscriber lines (DSLs). Various digital technologies provide customers with additional flexibility and enhanced services by utilizing frequency-division multiplexing and/or time-division multiplexing techniques to fully exploit the transmission capability of a subscriber loop. These newer DSL technologies provide digital service to the customer premises without significantly interfering with the existing plain old telephone service (POTS) equipment and wiring by utilizing portions of the available frequency spectrum not used by a POTS signal. These portions of the frequency spectrum are often referred to as “logical channels.” Logical channels within a subscriber line that carry digital signals are known as “DSL channels,” while logical channels within a subscriber line which carry POTS analog signals are known as “POTS channels.”
DSL technologies, such as but not limited to, integrated services digital network (ISDN), high-bit-rate digital subscriber line (HDSL), HDSL2, and symmetric digital subscriber line (SDSL), utilize different frequencies of the available frequency spectrum and therefore do not coexist with a POTS signal, which typically utilizes the 0–4 kilo-hertz (KHz) portion of the available frequency spectrum. These DSL technologies accomplish this functionality by frequency-division multiplexing (FDM) a single data signal onto a logical channel above (at higher frequencies than) the 0 KHz to 4 KHz frequency range used by the analog POTS signals. Such multiplexing techniques and terminology are common to those skilled in the art, and are not described in detail herein.
Several variations of new multiple channel DSL technology exist, such as, but not limited to, Asymmetric Digital Subscriber Line (ADSL), Rate Adaptive Digital Subscriber Line (RADSL), Very High Speed DSL (VDSL), Multiple Virtual Lines (MVL™), Tripleplay™, and ReachDSL™, with this group generally referred to as xDSL. Communications systems employing xDSL technology may multiplex a plurality of data signals and a single POTS signal onto a single subscriber line. An xDSL system employing frequency-division multiplexing would multiplex a plurality of data signals onto a corresponding plurality of logical channels, each logical channel utilizing a different portion of the available frequency spectrum. An xDSL system employing time-division multiplexing would multiplex a plurality of data signals onto a single logical channel with each different data signal allocated to a predefined portion of time in a predefined, repeating time period.
As xDSL technologies have developed over the years, a number of service providers have leveraged the local loop by enabling the transmission of voice calls over the existing DSL network via the DSL channel(s) rather than the POTS channel(s). For example, one or more service providers may combine to offer the following services to a customer premises: (1) normal baseband POTS over a POTS channel; (2) data services over a DSL channel; and (3) data voice services via a derived POTS channel, which is multiplexed with the DSL channel. In operation, the derived POTS channel is typically digitized, multiplexed with the DSL channel, and communicated to the CO via the local loop using one of the following, or other, protocols: voice over DSL (VoDSL); continuous bit rate (CBR); voice over Internet Protocol (IP) (VoIP); voice telephony over Asynchronous Transfer Mode (ATM) (VoATM); or voice over Frame Rely (VoFR).
Data voice services, voice over DSL (VODSL) services, derived telephony services, derived POTS voice services, etc. are typically implemented by providing an integrated access device (IAD) at the customer premises. Commercial implementations of an (IAD include the SuperLine™ series of IADs manufactured by Paradyne Networks, Inc. As known in the art, in general, an IAD interfaces with the local loop at the customer premises and integrates voice transmission and data transmission onto the DSL line. Typically, an IAD supports a number of analog POTS ports to allow connections for telephones, facsimile machines, key systems, and modems. An IAD also supports a number of ports to allow connections for telephones that support data voice (e.g., VoIP phone, etc.). An IAD also includes one or more data ports with multiple networking interfaces for supporting data communications via the DSL channel. In this regard, a typical IAD provides a single point of access at the customer premises that can simultaneously deliver POTS and other switch-related services to a telephone, derived POTS voice services to a properly-configured device (e.g., VoIP phone, etc.), and data services to a computing device.
A typical IAD, or similar customer premise equipment (CPE), may integrate analog voice services with derived POTS voice services in the sense that both services may be provided to separate ports in the IAD. For example, a typical IAD may be configured to provide derived POTS voice services to a VoIP telephone via one port and analog voice services to a telephone via another port (e.g., register jack-11 (RJ-11) connector). Thus, the two services are “integrated” in the sense that they are integrated within the CPE to separate ports. However, existing IADs do not integrate analog voice services with derived POTS voice services at a single port to a telephone.
Thus, there is a need in the industry for systems and methods for integrating analog voice services and derived POTS voice services in a DSL environment.